1. Field of the Invention
The present invention relates generally to devices and methods for incinerating industrial waste compounds, and more particularly to devices that are installable within the exhaust ducting of industrial processing equipment to incinerate organic industrial waste products and having a flame baffle disposed within the combustion zone to aid in the incineration process.
2. Brief Description of the Prior Art
Chemical processes used in the manufacture of microelectronic devices as well as other industries emit waste streams of materials known as volatile organic compounds (VOCs) usually in low concentrations of an exhaust air stream. Such concentrations can be in the order of a few parts per billion to several percent. The majority of the waste streams however, contain VOC waste products that are in concentrations of fifty to 1000 parts per million. Such waste streams account for the release to the environment of thousands of tons per year on a global scale. The detrimental effects of these releases have become better understood in recent year and efforts to reduce them through better processing to minimize both the use and amount of VOCs released have become important. Even with these efforts, unacceptably high levels of VOCs are released on a daily basis. Equipment known as abatement devices are used to adsorb/absorb, react, recover, and convert the VOC wastes to prevent their release. Recent studies in states such as California show that waste streams containing low concentrations of VOCs can be very expensive to process. Often a limiting factor for regulatory agencies to require the use of abatement devices is the extremely high cost of converting each pound of VOC waste. Another is the production of reaction products which are as undesirable to release as the VOC being processed. One example of the latter is the production of oxides of nitrogen when flame is used to incinerate or otherwise convert VOC wastes. The South Coast Air Quality Management District located in Southern California currently limits the creation of no more than two pounds of oxides of nitrogen for each ten pounds of VOC destroyed.
Unlike U.S. patent application Ser. No. 07/438,678 filed in Nov. 17, 1989 by myself and Jay R. Walker, the present invention does not attempt to measure or quantify the VOC's contained in a waste air stream. That technique of my prior application requires that the VOC concentration be high enough to have some positive fuel value or contain a VOC waste in sufficient concentrations as to require additional fuel to induce pyrolytic decomposition. Such concentrations are in the range of 0.1-1% before they become significant. Waste streams found in industry usually contain 0.001-0.1% thus severely limiting the application of the prior device. A national sampling of the electronic, chemical, and pharmaceutical industries showed that waste streams containing VOC concentrations of 0.1% or greater were the exception to the rule. Additionally, the nitrogen oxides produced by that prior device were in the order of several hundred parts per million, an unexceptionably high concentration. The present invention is designed to control the conditions of the reaction zone to allow greater than 90% conversion of VOC's and generation of nitrogen oxides equal to or less than 0.000025%. Using the criteria of 20% nitrogen oxide generation described earlier, waste streams containing less than 0.000125% of VOC's can be processed with this new device and still meet the most stringent existing regulations. A device patented by Brewer et al. in 1977, described in U.S. Pat. No. 4,038,032, uses the temperature measured at the output port of the combustion chamber to control the fuel flow to the burner. Also Brewers device is designed to operate in a continuous mode and as such, the output temperature can vary as a function of system heating and cooling of air passing over the outside of the combustion tube. This variation has been measured to be in excess of forty degrees centigrade which interferes with proper monitoring of the reaction zone temperature.
Further prior art known to the applicant includes U.S. Pat. No. 4,661,056, issued Apr. 28, 1987 to Earl Vickery (one of the inventors of the present application) and Mark Yates. Other relevant prior art includes U.S. Pat. No. 4,444,735, issued Apr. 24, 1984 to Birmingham et al.; U.S. Pat. No. 4,038,032, issued Jul. 26, 1977 to Brewer et al.; U.S. Pat. No. 4,305,724, issued Dec. 15, 1981 to Micko; U.S. Pat. No. 4,464,653, issued Aug. 7, 1984 to Winner; U.S. Pat. No. 4,123,220, issued Oct. 31, 1978 to Bond et al.; U.S. Pat. No. 3,993,449, issued Nov. 23, 1976 to Childs; and U.S. Pat. No. 3,893,810, issued Jul. 8, 1985 to Lientz.